It isn’t the only facility in Saddam Hussein’s clandestine nuclear-weapons program. He has built more than a dozen such plants across the country. And there is evidence that Iraq has also worked on projects to build a nuclear reactor that could help him produce weapons-grade plutonium.

Either the uranium or plutonium could provide Saddam with what he needs to build a bomb -- and much sooner than many in the West think. "With access to nuclear materials, Iraq could produce a nuclear weapon within one year," a top U.N. weapons inspector told me recently in Vienna.

Western governments have known for years that Saddam has pursued weapons of mass destruction, including a nuclear bomb. In fact, after the Gulf War U.N. arms inspectors uncovered thousands of documents revealing a vast and extensive nuclear-weapons program.

Unlike the clear signs of chemical or biological weapons, however, U.N. inspectors could not find conclusive evidence that Iraq was on the verge of joining the Nuclear Club. This resulted, if not in complacency, then at least in a feeling that the West, especially America, had breathing space.

There is a widespread perception that after the Gulf War Iraq’s nuclear research was essentially "capped," because U.N. weapons inspectors were on the ground, preventing Iraq from restarting weapons programs that were destroyed or damaged during the war.

But during an investigation for Reader’s Digest, I discovered evidence that indicates that the infrastructure for Saddam’s nuclear R&D program is more intact than previously believed. Al-Ubur is one example. The Iraqi government claims the factory builds tractor parts.

But U.N. weapons inspectors who have visited Al-Ubur as recently as last year noted the factory was equipped with a high-capacity power source and its own water-purification plant -- two telltale signs of "calutrons," huge particle accelerators that are used to enrich uranium. This technology, while obsolete in the West, is nevertheless a functional and proven uranium-enrichment system. "We are worried what the Iraqis can do in this facility in the future," one U.N. weapons inspector says.

Another disturbing piece of evidence about Saddam’s nuclear program was provided to me by officials of the leading opposition group, the Iraqi National Congress (INC), during a recent trip to Europe. Early in 1994 an Iraqi nuclear technician who had worked on uranium-enrichment programs defected to the INC in northern Iraq, carrying an extensive collection of documents, including rough, hand-drawn diagrams for a nuclear reactor Iraq planned to build with components probably purchased from China. He also provided detailed reports on ostensibly civilian manufacturing facilities where secret nuclear-weapons research took place for more than a decade.

According to the INC, this man (whose identity cannot be revealed because of family in Iraq) was debriefed by the CIA for two months at an embassy overseas.

Yet details from the debriefing were apparently never passed on to such presumably interested parties as the International Atomic Energy Agency (IAEA) or UNSCOM. Even the then-head of the CIA's nonproliferation center, Gordon Oehler, doesn’t recall receiving detailed reports on the defector’s information. (When asked to comment for this story, the CIA declined.)

I showed the defector's information to nuclear experts at the IAEA in Vienna, and to U.N. weapons inspectors in New York. While they insisted before these meetings that they would not confirm a defector’s reports, they expressed surprise that so much of the information was new to them.

Items they were familiar with, such as details of Iraq's little-known laser uranium-enrichment program, and the names of scientists working at various nuclear establishments, added to the credibility of the defector's information.

The IAEA had long monitored Iraq for evidence of a nuclear reactor, using sophisticated environmental sampling gear that could pick up heat signatures and other telltale signs from an operating nuclear plant. They never detected such activity. The defector’s report gave a coherent explanation why:

The reactor could be dismantled and transported easily, its components hidden at sites throughout the country. It would then be undetectable to inspectors. One IAEA official told me that while they never uncovered evidence of the nuclear reactor’s existence, Iraqi officials at one time admitted to building experimental reactor fuel assemblies prior to the Gulf War, but claimed they had been destroyed.

The defector’s report said the Iraqis had manufactured 200 uranium fuel bundles (almost enough for an entire reactor core) before the war and hid them from U.N. inspectors. The uranium fuels the nuclear reaction and generates plutonium as a by-product.

While the IAEA has never found these bundles, drawings of their planned core design, provided by the Iraqis to the IAEA, matched the defector’s reactor sketch. The defector’s documents included information about the reactor’s uranium fuel rods and a fuel-fabrication facility which tracked with information the IAEA had previously uncovered.

Former IAEA inspector David Kay says that while this type of reactor is not the ideal way to obtain weapons-grade fuel, it does produce plutonium. "Are there advantages to plutonium over enriched uranium as a weapons material? Yes: it's a lot easier to make smaller warheads you can put on missiles," says Kay.

And now Iraq is free to pursue its nuclear ambitions without restraint. It has blocked UNSCOM and IAEA investigators from carrying out their work since last August. Those inspectors left Iraq on December 16, just hours before the Desert Fox bombing campaign, and U.N. officials admit privately that they are unlikely to return any time soon.

An IAEA official confirms that Iraq maintains a vast nuclear-production capability, only small portions of which were subject to U.N. monitoring. With the end of the U.N. inspections Saddam is free to bring his nuclear gear out of hiding and resume a crash program to build the bomb. "The threat is in the present and the future," the top IAEA official said in an interview.

Despite American knowledge of these Iraqi capabilities--and the almost-daily bombing runs by U.S. and British pilots -- most of the facilities where Iraq is storing or operating this equipment are still standing.

In fact, an intelligence source said that the U.S. Joint Chiefs removed several weapons facilities from the target list for the Desert Fox bombing campaign last December, due to "environmental" concerns. "The fear was that nuclear or biological material could leak into the atmosphere and cause a widespread disaster," the source said. (The Joint Chiefs deny that they did this.)

Such considerations may have shaped U.S. bombing policies, but those who have worked with Saddam on his weapons projects say that fear of a disaster does not register with him. Any such concern is overwhelmed by this desire to hold nuclear weapons over his enemies. In the end, says Dr. Khidhir Hamza, former head of Iraq’s nuclear-weapons program, Saddam’s logic is frightening and simple: "He is hated by his neighbors, and has become an international pariah. Saddam without the bomb is dead."